Operate your MTV-9 at 2500 RPM rather than 2700. I have done the EASA approved noise test on the MTV-9 on a 182 amphibian. 2500 RPM met their requirement for quiet which the 2700 certainly does not. The climb performance difference between 2500 and 2700 is not significant. The measurement of noise of the aircraft as a whole was made at the arequired point, 2 km from brake release, with a specified climb after liftoff. What I noticed, as my altitude was also carefully measured, was that the difference in altitude achieved at that point was 60' more at 2700 than 2500. 60' is negligible for your performance, particularly if your noise output is no longer offending your neighbours, 'cause you reduced RPM.
On my MTV-15 on my Lycoming O-360, I find that my best performance is achieved with the engine 2" oversquare. The MT 3 blade props have a greater "activity factor" so a slower RPM can be beneficial.
On a related observation, consider your power off glide with a windmilling MTV prop, you may find a more steep glide. Consider selecting full course pitch, if a glide is required. Go up high, and experiment.